Rust inhibiting composition



Patented July f FFICE and Charles E. Paxton, .lamesburg,

N. 1.,assignors to Standard Oil Development Company, a corporation of Delaware Application July 24, 1948, Serial No. 40,505

3 Claims. (01. 252- -sa.4)

This invention relates to rust inhibiting compositions, especially to compositions of matter for arresting. preventing and inhibiting the corrosion of metals, and more particularly, for the preservation of articles fabricated from iron, steel and other ferrous alloys. The present appli'cation is a continuation-in-part' of accompanying application Serial Number 622,102, filed on October 12, 1945, which became abandoned on July 27, 1948.

The corrosion of a metal, particularly a ferrous metal. is a problem which has existed since the making of metallic articles and tools began. Many corrosion problems arise calling for special consideration, such, for instance, as the handling of large volumes of acid; however, by far the greatest corrosion problem is in connection with ferrous metals and their proclivity for corrosion when exposed to even normal atmospheric conditions. Active corrosion of metallic surfaces has been impeded, arrested, or'prevented by coating the metallic surface with an inert, impervious film applied to the metallic surface b dipping, spraying, brushing or swabbing.

An object of the present invention is the formation of an oily, preferably non-drying composition of matter for arresting or inhibiting the rusting of ferrous metals. Another object is the preparation of a composition containing multifunctional agents of a corrosion preventive, antioxidant and dispersant character.

Still another object is the preparation of compositions of this type which may be used not only as protective coatings but which also may be employed if desired as internal combustion engine lubricants. Such lubricants combine the advantages of promotin general engine cleanliness during use and of inhibiting rusting and related corrosion caused by the presence of moisture and of acidic fuel residues during periods of non-use. When operating internal combustion engines in climates having high humidity it is not uncommon for rusting to begin in an engine within as short a period of time as one hour after the engine is shut down. The advantages of a lubricating oil composition having the property of preventing rusting under such conditions are obvious. For related reasons, compositions suitable for lubrication or for protective coating of firearms, ordnance equipment, industrial machinery, etc., can'be prepared in accordance with the present invention. The above objects of the invention, as well as other objects. will be ap- 2 parent to those skilled in the art upon reading the following description.

The compositions of the invention are therefore improved oil-compositions which contain the usual constituents of an oily solvent or protective base material which is generally a mineral oil product such as Stoddard solvent, gas oil, lubricating oil, wax, petrolatum or mixtures of the same. To this base material are added the specific anti-corrosion agents which form the subject matter of the present invention. Synthetic oils, e. g., esters such as dibasic acid esters and polyethers may be employed as the base oils.

The anti-corrosion agents contemplated according to the present invention are aliphatic carboxylic acid partial esters of polyhydric alcohols, said alcohols having at least three hydroxyl groups, these preferably though not always necessarily being branched from a single carbon atom, or still more accurately the hydroxy esters of such alcohols. These esters are characterized by having at least one free hydroxyl group in the molecule, and where possible it is preferred to have two or more free hydroxyl groups in the molecule of the ester. Alcohols which may be used as starting materials for producing the esters useful in making the compositions of the present invention are exemplified by pentaerythritol, di-pentaerythritol, poly-pentaerythritol, and trimethylol propane. Glycerol and erythritol also may be used, although they are not quite as effective. Other alcohols having a tertiary or neo-carbon atom structure similar to that of the pentaerythritols may also be used. With these polyhydric alcohols of three or more OH groups, it has been discovered that the mono-esters of the polyhydric alcohol are very proficient and effective anti-corrosion agents. The esterification of each succeeding OH group diminishes the effectiveness of the partial ester as an anti-corrosion agent until the completely esterified polyhydric alcohol shows little or no anti-corrosion properties. Thus the diester is usually somewhat less potent than the mono-ester, and the tri-esters or tetra-esters are quite inactive.

The acids useful for the esterification of the polyhydric alcohol compounds are those fatty acids having from about 10 to 22 carbon atoms which are commonly combined with glycerol in naturally occurring animal and vegetable oils and fats and which are derived therefrom upon saponification thereof and are exemplified by the fatty acids derived from stearin, fish or whale oils, animal fats, and vegetable fats or oils, and the like. The list of preferred esterifying materials includes fatty acids, such as, capric, lauric, myristic, palmitic, oleic, linoleic, linolenic, ricinoleic, stearic, dihydroxystearic, eleostearic, erucic and behenic. The moderately unsaturated long chain acids such as oleic acid are particularly suitable, also hydrogenated or partly hydrogenated. or oxygenated fatty acids. It is also contemplated that mixtures of the foregoing acids may be used in the esterification of the polyhydric alcohols. It is also often advantageous to employ mixtures of such acids with low molecular weight acids such as acetic, propionic, glycolic, lactic, etc., to produce mixed esters. These should be of short chain length, not exceeding 4 carbon atoms. The long chain acids have the advantage of imparting some oil solubility to the ester, although the partial esters are only very sparingly soluble in oil because of the free hydroxyl groups they contain. Esterification of some of these with a, short chain acid tends to improve oil solubility.

The anti-corrosion agents of the present invention' are made by reacting one mol of the polyhydric alcohol with preferably only one or at most two mols of carboxylic acid or carboxylic acid mixtures either in the presence of or absence of a catalyst as is well understood by those skilled in the art. The catalyst may be acidic, for example, sulfuric or phosphoric acid, or alkaline as, for instance, sodium hydroxide, or it may be a salt such as stannous chloride. The ingredients are commingled and heated in a kettle or other container, preferably closed and equipped with suitable agitating means at a temperature of 125300 C. until the esterification reaction reaches completion. It is frequently desirable to maintain an atmosphere of inert gas, such as nitrogen or a carbon oxide over the reacting mass. This may be done by passing an inert gas over or through the reacting mass in order to assist removal of the water of reaction and prevent discoloration of the esters formed or the reaction may be carried out in a refluxing hydrocarbon solvent with means provided for trapping out the water formed. It may be advantageous in some instances to modify the esters by introducing ether groups, for example by reaction with ethylene oxide.

The compositions of the present invention, as before stated, comprise an oleaginous base, preferably of mineral oil, although vegetable or animal oils or mixtures of oils may be used as the base, blended with a minor proportion of a 'carboxylic acid partial ester of an aliphatic polyhydric alcohol having at least three hydroxyl groups preferably branching from a single carbon atom. The compositions are produced by blending from 0.1% to preferably 0.5 to 3%, by by weight of the ester in the oleaginous base, using heat and stirring if necessary. The present invention is based upon the further discovery of a synergistic effect of oil soluble metal sulfonates when combined with the esters described above. It is highly desirable to include one or more of such sulfonates as auxiliary agents in the preservative composition in proportion of about 0.5 to 10% by weight, preferably 0.5 to 3%. These include especially the oil soluble sulfonate soaps, of alkali or alkaline earth metals, such as calcium or sodium soaps of mahogany sulfonic acids. For some purposes other known rust inhibitors may be used also, such as metal xanthates,

metal phenolates, metal phenol sulfides, metal naphthenate, metal organo phosphates and thiophosphates, organic bases, vegetable or animal fatty oils, etc. Wool grease (degras) is a particularly suitable additive when aresidual coating which will adhere well to the metal is desired. See the patent to Lebo No. 2,182,992.

Metal sulfonate salts of the types mentioned are particularly desirable, in combination with the partial esters of pentaerythritol in rust preventive crankcase lubricants and also in rust preventive coating compositions. These should be employed in most cases. Additional salts which may be used include barium tert.-octyl phenol sulfide, calcium diamyl phenate, aluminum stearate, zinc naphthenate, tin lauryl phenol sulfide, nickel amyl xanthate, reaction product of P285 and barium tert.-amyl phenol sulfide, zinc diisopropyl salicylate, barium dioctyl thiophosphate, calcium amyl phenol thiophosphate, calcium qctadecylate, and the like.

For special purposes, such as to enable the composition to dislodge water from metal surfaces, alkylol amines, alcohols, esters, ethers. ether alcohols and the like may be incorporated in the composition. Also, one or more of the free hydroxy groups present in the hydroxy esters of the present invention maybe reacted with phosphorus sulfides or oxides, thio acids, xanthates or carbamic acids to produce multi-fimctional corrosion preventives, rust inhibitors, de-

tergents and anti-oxidants.

Because of their potent rust preventive properties the esters of the present invention may also be employed in fuel compositions such as Diesel fuels, domestic and industrial heating oils, ker0- sene, gasoline and the like. They are primarily useful, however as crankcase lubricants for internal combustion engines, and as slushing oils or coating compositions such as are applied to machined or polished ferrous metal surfaces to prevent rust.

The efiiciency of rust preventive compositions is best evaluatedby actual service or exposure tests, although certain standard laboratory tests, of which the humidifier test is the one most employed, may be used for rapid evaluation.

Test procedure Sand blasted panels of hot rolled steel are dipped into slushing compound samples, then maintained vertically in a box for 16 hours under ordinary room conditions to allow the rust pre ventive film to reach an equilibrium condition. Compounds containing petrolatum or Waxes are applied at temperatures above their melting point and fluid products are applied at room temperatures. The coated panels are then placed in an upright position in a humidifier chamber maintained at -l20 F. where they are subjected to continuous moisture condensation. The test pieces are spaced in the cabinet in such a manner that they do not come in contact with each other. The time, in hours, for a panel subjected to these conditions to develop initial evidence of rusting is observed and recorded as the resistance life of the coating composition.

According to Government specification AN-VV- (3-5761) the minimumresistance life for a coating composition tested under these conditions is set at hours.

The following examples illustrate the rust preventive effectiveness of compositions of the present invention on the basis of the above tests.

Example I 0 Base Oil Base Oil+1% pentaerythritol monooleate Base Oil+1% calcium sullonate Base Oil+0.5% pentaerythritol monooleate and 0.5% calcium sulionate Base Oil+2% pcntacrythritol monooleate Base Oil+2% calcium sulfonate Base Oi1+0.5% pcntaerythritol monooleate and 1% calcium sulfonate. Base Oil+0.5% penis-cry ritol monooleate and 2% calcium sulfonate. Base Oil+1% pentacrythritol monooleate and 0.5%

calcium sulionate Base Oil+1% pentaerythritol monooleate and 1% calcium sulionate Base Oil+1% pentaerythritol monooleate and 2% calcium sulionate Base Oil-{43% pcntaerythritol monooleate. Base Oil+1% calcium suli'onate Base Oil+2% pentacrythritol monooleate a calcium suli'onatc Base Oil+2% pentaerythritol monoolea calcium sull'onate 1 It will be noted that in tests Nos. 7, 10, 13 and 14. the tests were discontinued after 312 hours with no incipient. rusting. The total of ester and sulfonate was 2.5% in itleist No. 7, 3% in No. 10. 2.5% inNo. 13, and 4% in No.

With as much as 3% of the individual components,

protection against rusting was obtained for a maximum of only 96 hours. The combined inhibitors, even in smaller total quantities, are much more eirectlve than would be expected from their individual inhibiting powers. These data are represented graphically in the drawing. It will he noted particularly that after the combined inhibitors exceed 1%. they are far more effective than either component alone and far beyond the expected additive eflect of the combined inhibitors. Where the pentaerythritol ester is added to the extent of at least 1% by weight, based on the total composition, the further addition of as little as 0.5% of the sulfonate produces a very satisfactory rust inhibitor. Where the quantity of ester is only 0.5 0 apparently the sulfonate should be in excess of 1%. pre eirahly about 2%. although the data are not entirely conc usive.

Escample II A typical naphthenic lubricating oil of S. S. U. viscosity at 210 F. was tested in the same manner as in Example I.

Test

No. n

Base Oil 1 Base 0il +3% glycerol trioleate 4 Base O1l+3% pentaerythritol monooleate mono- 200+ ac c. Base Oil +3% pentaerythritol monooleatc Petrolatum Petrolatum-l-lV pentaerythritol monoolea Petrolatum+l% di(pentaerythritol monooleate) v Example IV Dioctyl sebacate, an ester which is known to have good lubricating qualities, was tested with results as follows:

Test No Hours 22"... Dioctyl scbacate 23..... Dioctyl sebacate+3% trimethylol propane 200+ 24..." Dioctylsebacate+3% B-hydroxyethyl ether oi ponta- 200+ erythritol monooleate. 26. Dioctyl scbacate+l% degras and 1% sodium sul- 24 one a. 20.-... Dioctyl sebacate+1% degras, 1% sodium sulfonate 214 and 1% pontaerythrltol monooleate.

Example V The synergistic action of pentaerythritol' mono- I oleate and the sulfonates is further illustrated and emphasized by the following:

Mineral oil of 120 S. S. U viscosity at 210 F.,

having a viscosity index of about 105, being of the same general specifications as the oil of Ex-,.

ample I but taken from an entirely difierent supply, was subjected to the following humidity cabinet tests with the various inhibitors indicated:

Hours 27 Base Oil Less than 1. 28 Base 0 +05% calcium sulionate Less than 24. 29. Base Oil+0.5% sodium sulfonate, Less than 24. 30. Base Oil+1% calcium sulfonate 24-48 3l Base Oil+1% sodium sulionate 24-48. 32". Base 0il+0.5% pentaerythritol monooleate. Less than 24. 33 Base Oil+0.5% pentaerythritol monooleate 200+.

and 0.5% calcium sulfonate.

34"... Base 0il+0.5% pentaerythritol monooleate 200+.

and 0.5% sodium sulionate.

35. Base 0il+1.5% pcntaerythritol monooleate 48.

36"... Base 0il+l.5% pentaerythritol monooleate 412.

and 0.5% calcium sulfonate.

37"". Base Oil+l.5% pentaerythritol monooleate 100.

monolactate.

3S. Base 0il+i.5% pentaerythritol monooleate 300+. monolaotate and 0.5% sodium sulfonatc.

above data. The monooleate monolactate ester shows good results which further justify the conclusion mentioned previously that. the mixed partial esters, where one esterifying group is a short chain group, may be quite as useful as the monoesters, in some cases at least. In this example, total quantities as low as 1% of sulfonate and partial ester were highly effective.

By adding wool grease (degras) to any of the above compositions, an excellent rust-proofing coating. composition may be prepared. A light hydrocarbon solvent may be used in lieu of hibricating oil. The use of degras for giving body to a rust preventive composition is well known per se as shown in the Lebo patent mentioned above but in combination with the ester, and especially with a. small amount of ester and sulfonate, the rust-proofing properties are outstanding. The proportions may vary, but about 0.5

to 3% of the ester, 0.5 to 10% of sulfonate and Even with as long an esterifying chain as the oleic radical, the solubility of the partial esters may not be too good in some oils or hydrocarbon solvents. The use of the sulfonates, which are highly oil soluble, makes it possible to obtain the,

required rust inhibiting properties with the small quantities of the partial esters which will readily dissolve. The oil solubility of the partial esters may be improved by esterifying an additional hydroxyl group on the polyhydric alcohol with a short chain acid such as lactic acid, or acetic acid,

' or by etherification with a short chain alcohol radical, by conventional methods.

It will be noted that it is desirable that the ester shall (1) be soluble in the proportions used,

and (2) have one and preferably two or more.

unesterified hydroxyl groups. These properties are somewhat incompatible, hence it is desirable either to improve oil solubility by further partial short chain esterification (which reduces the number of free hydroxyl groups on the polyhydric alcohol) or, which is preferable, to supplement the inhibiting effect of the partial ester, which is limited in effectiveness by its limits as to oil solubility, by using a synergistic inhibitor selected from the metal sulfonates, preferably calcium and/or sodium sulfonate. As with previous examples, degras, wax, and the like may be added where a residual coating is desired after the hydrocarbon oil or solvent has evaporated.

Example Vi An excellent hydraulic oil which passed the rather severe U. S. Air Forces test AN--7 for airplane rust preventive hydraulic fluids was prepared using as a base oil an oxidation inhibited mixture of substantially equal parts of highly acid treated Coastal (naphthenic) gas oil and a phenol and acid treated naphthenic transformer oil of about 60 'S. S. U. viscosity at 100 F. This oil contained a small amount of a commercial viscosity index improver of the acrylate polymer type in order to raise the index to about 130. 0.2% 2,6-butyl 4-methyl phenol was used as the oxidation inhibitor in the base oil. The base oil had a viscosity of about 43 S. S. U. at 100 F.

To 94 parts by weight of the above oil, there were added 6 parts of a commercial 50-50 oil solution of sodium sulfonate, thereby incorporating about 3% of the sodium sulfonate in the oil. Calcium sulfonate can be used if desired. To this was further added 0.5% of pentaerythritol monooleate and a further quantity, about 0.2%, based on the total composition, of the alkylated phenol oxidation inhibitor mentioned in the preceding paragraph, thus raising the oxidation ins I hibitor content to about 0.4%.

In general, 90 to 98 parts by weight of a light mineral oil or synthetic oil of low viscosity such I as 35 to 100 S. S. U. at 100 F. and of high vis-' or calcium or a mixture, 02% to 3% of pentaerythritol monooleate, about 0 to 1% of oxidation inhibitor and 0 to 1.0% of viscosity index improver.

While numerous esters of complex alcohol have been proposed in the for lubricating oils, including some of the pentaerythritol esters, esters of hexitols, and the like, the specific combination of a small amount of long chain acid partial ester of a trior tetrahydroxy alcohol, especially pentaerythritol monooleate or its equivalent, with or without addition of short chain ester or ether groups, with a small amount of an oil soluble alkali or alkaline earth metal sulfonate as a potent rust inhibitor in mineral base oils, petrolatum and the like, for lubricating and/or coating ferrous metal surfaces characterizes the present invention. The range of proportions may be from about 0.1 to about 10% of the ester and a similar range for the sulfonate, based on the total composition. For lubricating oil compositions, the narrower limits of 0.5% to 3% of each are specifically preferred since larger quantities of ester are commonly insoluble and larger quantities of the sulfonate are commonly unnecessary. Quantities of either, smaller than 0.5%, are useful but less effective. The mixed esters of low molecular weight carboxylic acids and long chain acids also maybe used as previously indicated.

It will be understood that other conventional 7 .grade containing 0.5 to 3%, based on the total composition, of a mono-oleic ester of pentaerythritol, 0.5 to 3% of an oil soluble petroleum sulfonate selected from the class which consists of sodium and calcium sulfonates, and 0 to 1% of degras.

2. Composition according to claim 1 in which the monooleic ester of pentaerythritol also con- .tains one lower carboxylic acid esterifying group of not more than 4 carbon atoms in chain length.

3. A rust inhibiting composition consisting essentially of a mineral base oil of lubricating grade containing 0.5 to 3% by weight of pentaerythritol monooleate and 0.5 to 2% of oil-soluble calcium petroleum-sulfonate.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,182,992 Lebo Dec. 12, 1939 2,371,333 Johnston Mar. 13, 1945 2,398,193 Sharp Apr. 9, 1946 2,410,652 Griifin Nov. 5, 1946 2,417,281 Wasson Mar. 11, 1947 2,430,058 Klaber Nov. 4, 1947 2,434,490 Duncan Jan. 13, 1948 2,479,424 Sproule Aug. 16, 1949 2,482,517

Schiermeier Sept. 20, 1949 prior art as additives 

1. A RUST INHIBITING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL BASE OIL OF LUBRICATING GRADE CONTAINING 0.5 TO 3%, BASED ON THE TOTAL COMPOSITION, OF A MONO-OLEIC ESTER OF PENTAERYTHRITOL, 0.5 TO 3, OF AN OIL SOLUBLE PETROLEUM SULFONATE SELECTED FROM THE CLASS WHICH CONSISTS OF SODIUM AND CALCIUM SULFONATES, AND 0 TO 1% OF DEGRAS. 